Cosmetic formulations applied to the skin and must have four key functions, (1) providing the cosmetic benefit sought (emmoliency, humectancy, smoothing, sun protection and the like; (2) provide cosmetic elegance when so applied; (3) be free of undesired reactive species like free vinyl monomer; and (4) be cost effective. The cosmetic chemist has long sought after this combination of properties.
Historically, the selection of materials that provide the oil phase for emulsions, serums and lotions have been made from mineral oil, petrolatum, naturally occurring oils and fatty esters. These materials while well used lack the ability to modify the feel, flow and film forming properties on the skin.
In making polyesters, one can either add all reactants, or pre-esterify the individual reactants followed by the reaction with diacids. We have learned that the pre-esterification of the intermediates followed by the reaction with diacids results in highly desirable polyesters, while reacting all raw materials together results in a gel.